Seismic on the edge—the Speculant 3D Transition Zone Seismic Survey

Abstract

The Speculant 3D Transition Zone (TZ) Seismic Survey was acquired by Origin Energy in the Otway Basin, about 30 km east of Warrnambool, Victoria, during November and December 2010. The objective of the survey was to fill a data gap between existing marine and land 3D seismic surveys. Although the survey covered a small surface area, it included part of the Bay of Islands Coastal Park, dairy farms, southern rock lobster fishing grounds and the migration route for the Southern Right Whale. Numerous exclusion zones were required to address a variety of stakeholder concerns, avoid environmentally sensitive areas, combat a physical landscape dominated by 60 m sea cliffs and the large Southern Ocean surf. These access restrictions required the innovative use of modern seismic technology to enable a survey that could simultaneously record onshore and offshore without a physical connection between recording systems. On land a GSR cable-free recording system was used for the first time in Australia, eliminating the need for any line preparation or vegetation clearing. Offshore an ocean bottom cable system was used. The survey employed smaller sources than traditionally used in the region. A 900 in3 generator–injector airgun array was used offshore while a single Vibroseis unit was used on land. This paper shares the lessons learnt during the planning, approval and acquisition of the Speculant Seismic Survey with the steps taken to reduce the operation’s footprint while maintaining data quality.